Il8 BIOCHIMICA ET BIOPHYSICA ACTA VOL. 4 (1950) 



SOME EVIDENCE ON THE 

 FUNCTIONAL ORGANIZATION OF THE BRAIN 



by 



HAROLD E. HIMWICH 



Medical Division, Army Chemical Center, Maryland {U.S.A.) 



"With health, the assertion is that each person's normal thought and conduct are, 

 or signify, survivals of the fittest states of what we may call the topmost "layers". Now 

 suppose that from disease the normal highest level of evolution (the topmost layer) is 

 rendered functionless. This is the dissolution ... I contend that his mental symptoms 

 are survivals on the lower, but then highest, level of evolution" (remaining in function). 



So wrote Hughlings Jackson in 1884^. One type of evidence for such an evolution- 

 ary concept involving a hierarchy of levels is observed by studying behaviour following 

 a series of surgical sections of the brain. A transection below the medulla gives rise to 

 the spinal animaP, a decapitated preparation kept alive by artificial respiration but 

 still responding to stimulation with primitive though appropriate muscular actions. 

 A painful stimulus applied to the foot pad, for example, evokes flexion of that leg, a 

 movement that makes for survival as the leg is withdrawn from harm. 



The decerebrate animal produced by cutting through a higher level^, namely the 

 lower portion of the midbrain and therefore retaining the medulla reveals a release of 

 the antigravity muscles permitting an abnormal sort of erect standing called decerebrate 

 rigidity. The decorticate animal with extirpation of the highest portion of his brain 

 only, expresses sham rage, a release of emotional patterns from cortical control^. Both 

 decerebrate rigidity and sham rage may appear spontaneously or may be evoked. These 

 three sections of the neuraxis reveal patterns of behaviour which are functional in the 

 intact organism but are modified by anatomically higher areas, of later development 

 which facilitate more delicate sensory perception and finer execution of movement. 

 For the organism to take advantage of these improved capacities the behaviour of the 

 lower portions of the brain must be subjected to the inhibition as well as the reinforce- 

 ment of the higher planes and when their influence is removed we see a release of function 

 in the lower areas, a result of loss of restraint. Strong support for the observation that 

 inhibition is a function of the brain has been afforded by the physiological experiments 

 of DussER DE Barenne AND McCuLLOCH^ who demonstrated thst stimulation of one 

 cerebral area suppresses activity in another. 



For another type of evidence we must turn to an examination of man for an oppor- 

 tunity is afforded to study the human brain when sections are made in a functional 

 manner. An example is observed during hypoglycemia when a temporary "dissolution" 

 of the brain is a result of excessive insulin^. The behavioural phenomena observed may 

 be allocated to certain cerebral areas. In fact, the signs exhibited are those that might 

 References p. 125. 



